1. Field of the Invention
The present invention relates to a method for starting an operation of a data storage unit equipped with an actuator arm which supports a flexible cable for data transfer connected between the transducer and the control circuit of the data storage unit. More particularly, the invention relates to a start method which makes it possible to execute early the access tension which a flexible cable gives to an actuator arm.
2. Description of Related Art
In a quest of user friendliness, the computer system in recent years is even further shortening the time needed to use of the computer system after power is turned on. In such environment, magnetic disk drives are used as the secondary data storage unit of the computer system and store an operating system and various application programs which are used in the computer system. Access to the magnetic disk drive has been recognized as a specific problem in shortening the time needed to use a host computer after power is turned on.
FIG. 1 is a plan view of a general magnetic disk drive. The magnetic disk drive 10 is a data storage unit which includes a rotary type magnetic disk 11 with concentric data tracks on which data is stored, a transducer (not shown) for reading or writing data from or to various tracks, a slider 12 with the transducer attached thereto, a suspension arm 13 having the slider 12 attached thereto so that bias force is applied in a direction in which the slider 12 approaches the surface of the magnetic disk 11, an actuator arm 14 and a voice coil motor (VCM) section 15 for locking the suspension arm 13 and for moving the transducer over a desired track position and maintaining it over the longitudinal center line of the track during read and write operations, a flexible cable 16 connected at one end thereof to the transducer and supported by the actuator arm 14, and a board 20 mounted with a control circuit section 17 connected to the other end of the flexible cable 16.
The magnetic disk 11 has a plurality of magnetic disks fastened to a spindle 19 and stacked at predetermined intervals. The magnetic disks 11 are rotated together with the spindle 19 by a spindle motor (not shown). A plurality of actuator sets each consisting of the transducer, the slider 12, the suspension arm 13, and the actuator arm 14 are stacked in correspondence with the respective surfaces of the magnetic disks 11 and constitute an actuator assembly 21. The actuator sets are integrally rotated over magnetic disk surfaces in directions of arrow A with stacked magnetic disks on which data can be read out or written to with the transducer are often called cylinders.
In order to position the transducer over a predetermined cylinder, a predetermined driving torque needs to be generated in the VCM section 15 to move the actuator assembly 21. The driving torque is computed from the relationship between the current cylinder position of the transducer and the cylinder position to which the converter is to be moved. Although the flexible cable 16 is connected to both the transducer supported by the actuator arm 14 and the board 20, it does not interfere with the rotation of the actuator assembly in the directions of arrow A. The flexible cable always gives the actuator assembly 21 tension in a direction of arrow B. Therefore, the driving torque for the actuator assembly 21, which is generated in the VCM section, needs to be set to a value compensating for the tension of the flexible cable 16.
However, the value of the tension of the flexible cable does not only vary with a cylinder position on the magnetic disk 11, but it also varies due to various major factors, such as operating conditions (temperature, humidity, voltage, etc.), elapsed years, and operating time. Therefore, the tension applied to the actuator assembly 21 by the flexible cable 16 needs to be successively corrected. In current magnetic disk drives, tension data is generated each time power is turned on.
Until a magnetic disk drive will be able to accept access from a host computer after power to the magnetic disk drive is turned on, there is always a need to perform a predetermined start operation. FIG. 2 is a flowchart showing a conventional procedure for starting the magnetic disk drive of FIG. 1. In step 50, power to the magnetic disk drive is turned on. Then, in step 51, an internal diagnostic program is executed to confirm whether there is anything abnormal in the function of the magnetic disk drive. After it has been confirmed that there is nothing abnormal in step 51, it is confirmed in step 52 that the spindle motor has been rotated and has reached a predetermined rotational speed. Next, in step 53, microcode which is stored on the magnetic disk for controlling the magnetic disk drive is read out to a memory. After the procedure in step 53 has ended, the actuator assembly is positioned over each cylinder to correct the tension data of the flexible cable (hereinafter referred to as tension data). Then the corrected tension data is stored on memory to form a table (step 54). After the procedure has been completed (step 54), the computer is at last able to have access to the magnetic disk drive to read out or write data (step 55). In a typical example of 3.5-inch magnetic disk drives, the start preparation from step 51 to step 53 takes 8 seconds and the generation of corrected tension data in step 54 takes 2 seconds, so that the host computer cannot have access to the magnetic disk drive for 10 seconds after power is turned on.
The object of the present invention is to provide a method of early use of a data storage unit which allows a computer system to be used as early as possible after turning on power to the computer system, including the data storage unit.
The principles of the present invention involve the use of the tension data of a flexible cable generated at the time of fabrication (hereinafter referred to as shipping-time tension data), to allow a host computer to have early access to a data storage unit. After power has been turned on, the host computer executes a diagnostic program. In order to complete the start operation early, the host computer requires early access to a data storage unit. On the other hand, during the start sequence of the data storage unit, generation of the corrected tension data of the flexible cable is always needed. However, at the stage immediately after power is turned on, the corrected tension data does not always have to be generated prior to the access of the host computer. Therefore, in the present invention, the start sequence of the data storage unit which must be executed prior to access by the host computer is first executed. After the start sequence has been completed, the host computer is allowed to have access to the data storage unit, and generation of corrected tension data is executed in parallel with the execution of the start sequence of the host computer.
In an embodiment of the present invention, after a start operation excluding generation of corrected tension data has been completed, if there is an access command from a host computer, it will be processed. The start operation excluding generation of corrected tension data is an operation that is always performed before accepting access commands, such as execution of an internal diagnostic program, start of a spindle motor, and reading of microcode to a memory.
In another embodiment of the present invention, previously generated tension data is stored on a non-volatile storage medium and read to memory during a start operation before generation of corrected tension data. When an access command is sent from a host computer before corrected tension data is generated, the torque which is generated in a voice coil motor (VCM) for positioning of a transducer is set by using the previously generated tension data. The previously generated tension data may be tension data generated at the time of shipment or old corrected tension data generated after shipment.
Still another embodiment of the present invention involves the case where the torque of the VCM cannot be appropriately set by previously generated tension data. When a transducer cannot be correctly positioned over a cylinder even after a predetermined time, the tension data is corrected to set a new torque for the VCM, and positioning of the transducer is again executed with the new torque for the VCM.
In a further embodiment of the present invention, following the end of the start operation excluding generation of corrected tension data, it is judged whether or not an unexecuted access command is present among the access commands from a host computer. If an unexecuted access command is present, it will be processed prior to generation of corrected tension data. If it is not present, generation of corrected tension data will continue to be executed. Therefore, generation of corrected tension data can be completed early, while giving priority to an access command from a host computer. The step of judging an unexecuted access command and the step of generating corrected tension data may comprise a plurality of steps.
In an additional embodiment of the present invention, even after the step of generating corrected tension data, the host computer is monitored for an access command. If an access command is present, it will be processed first. Therefore, until corrected tension data is finally generated, an access command from a host computer is executed prior to generation of corrected tension data, and corrected tension data is generated by utilizing a time when there is no access command.
A computer program capable of carrying out the aforementioned embodiments of the present invention is stored on the non-volatile storage medium of a data storage unit, and when power is turned on, the computer program is read out to a random access memory (RAM) as microcode and is then executed.